Patent GB-520587-A (GB)
Title: Improvements in or relating to automobile clutch and change speed controls
Filed: 1938-10-26
Abstract: 520,587. Controlling change-speed gearing and clutches ; fluid - pressure servomotor - control systems. BENDIX-WESTINGHOUSE AUTOMOTIVE AIR BRAKE CO. Oct. 26, 1938, No. 30918. Convention date, Oct. 28, 1937. [Class 80 (ii)] [Also in Group XXIX] A fluid-pressure motor 11, for actuating a motor-vehicle clutch-controlling element 8, is energized under the control of two automatic valves, one 44 responsive to engine-speed so as to disengage the clutch automatically at low engine-speeds, and the other, 49 actuated by the gear selecting mechanism so as to effect a disengagement and re-engagement of the clutch coincidental to a gear-shift, and mechanical or fluid-pressure operated means are provided to render the speed-responsive valve 44 inoperative to energise the clutch motor 11 when a predetermined ratio or ratios is or are established in the change-speed gear. By these means, complete or partial automatic clutch disengagement at low engine-speeds is precluded in, say, the two highest speeds of a transmission providing three or four speeds and reverse, whereby the possibility of the speed-responsive valve causing clutch-slip when travelling under load at low vehicle-speeds in these two speeds is prevented. Mechanical and fluid pressure gear-shifting systems are described, and in all cases the exhausting of the clutch-motor 11 for clutch re-engagement always takes place through the speed responsive valve 44, so that the rate of re-engagement in all ratios is always under the speed - responsive control. In the fluidpressure operated gear-shift mechanism shown in Fig. 1, selection amongst three striker-forks 15, 16, 17 is effected by a cross-shift motor 19, which turns an executive-lever 18 about the piston-rod 27 of a motor 22 which thrusts the lever bodily for establishing the speeds. Movement of the centre fork 16 in opposite directions from neutral provides second and high speeds, whilst both the outer forks 15, 17 move only in one direction from neutral, viz, to the left of Fig. 1, for establishing low speed and reverse respectively. Energization of the cross shift and gear establishing motors is effected by a multiple-valve unit 33, controlled by a slot-guided hand lever 10, and communicating with a compressed-air reservoir 31 through a reducing-valve 37. For establishment of second and high speeds, the hand lever 10 is moved to opposite ends of the slot 34, whilst movement of the lever in the slot 35 controls low speed and reverse, the latter having a safety-catch 42. The left-hand side of the gearestablishing motor 22, which only establishes second speed, receives its pressure-air directly from the selector-valve unit 33, through the pipe 25, whilst the right-hand side which acts for low and high speeds and reverse, receives its presure-air only through valves 40 or 41 opened by the cross-shift motor 19. The gearestablishing motor 22 also includes small neutralising pistons 29, 30 subject at all times to reservoir-pressure through a pipe 32. Clutch operation coincidental with gear-shifting is obtained by a valve 80, which, when lifted by cam surfaces 86, 87 on the gear-establishing piston rod 27, opens a reservoir pipe 91 directly to the clutch-motor 11 through a pipe 50, thereby disengaging the clutch. The executive-lever 18 has slight axial play on the piston rod 27 so that clutch-disengagement precedes executive movement of the lever 18. In the neutral and either end gear-position of the piston rod, the valve 80 is allowed to fall and re-engage the clutch by exhausting its motor 11 to atmosphere through the now open lower seating 81, a pipe 48, the speed-responsive valve 44 and an outlet 51. Clutch re-engagement is thus always under speed-responsive control. The latter comprises engine-driven centrifugal masses 57, Fig. 3, which, at a predetermined speed, move a sleeve 60 to the right, allowing one end 71 of a double valve to cut off communication between a pressure-inlet pipe 47 and an outlet-pipe 48, leading to the clutch-motor 11 through the gearcontrolled valve 81, whilst the other end 72 of of the double-valve exhausts the outlet-pipe 48 through ports 73 and a pipe 51, so that the clutch is allowed to engage. The pressure-pipe 47 of the speed-responsive valve 44 communicates with the reservoir-pipe 45 through a valve-unit 46, having a valve-member 101, Fig. 2, which is pressed downwardly into the open position by a spring 99. Whenever second or high speeds are selected by the handlever 10, Fig. 1, pipes 25 or 39, respectively, are put under pressure and either of them, through a common valve 92 and pipe 94, supplies pressure to the underside' of a diaphragm 98 in the valve-unit 46, thereby allowing the valve 101 to. close and cut off communication between the speed-responsive valve 44 and the pressure reservoir 31. The speed-responsive valve 44 is thus rendered ineffective for causing clutch disengagement in second or high speeds. In a modification, Fig. 4, not shown, the valve 46, Fig. 1, is omitted, and the double-valve 92 is connected to the conduits 20 and 21 of first-speed and reverse, instead of to the second- and highspeed. conduits as in Fig. 1. Thus fluid-pressure is only supplied to the speed-responsive valve 44 when the selector-lever 10 is moved into the low-speed or reverse position, and the valve 44 is ineffective for producing automatic clutch disengagement in second or high speeds. In a further modification, Fig. 5, change-speed selector-bars 210, 211 are manually shifted in the conventional manner by a lever 207, and have cam surfaces 276, 277, 278 for lifting valves 254, 269 to energize a clutch motor 212 from a compressed-air reservoir 214, whenever either bar is moved out of neutral and gear positions, whereby clutch disengagement and subsequent re-engagement is effected coincidentally with a shift-gear. The outlet-pipe 218 of a speed-responsive valve 213, which is similar to the valve 44, Figs. 1 and 3, communicates with the clutch-motor 212 through the lower seatings of both the shifter-actuated valves 254, 269 in series, whilst the inlet-pipe 217 of the speedresponsive valve communicates with the pressure-reservoir 214 through an additional valve 283 which is allowed to close whenever the selector-rod 210 moves to either gear position, viz, second- or high-speed from neutral, so that the speed-responsive valve 213 is ineffective for disengaging the clutch in second- or high-speeds. In the modification shown in Fig. 6, the two shifteractuated valves 254, 269 of Fig. 5 are combined into a single valve 332, which is opened whenever any of three selector-bars 291, 292, 293 is moved from a gear or neutral position, these three bars controlling respectively third and fourth speeds, second and first speeds, and reverse. The selector-bars have cam-notches 316 which, when the bars leave neutral or gear positions, raise balls 310, which act through camended drift-blocks 305, 306, 307 to lift the valve 332. As before, the outlet of the speed-responsive valve 296 leads to the clutch-motor 295. through the valve 332, whilst its inlet 301 leads to a pressure - pipe 299 through a valve 348, which latter is closed whenever the selector-bar 291 moves from neutral to gear positions, so that automatic speed-responsive clutch disengagement is prevented in third and fourth speeds. For actuating the valve 348, its stem 344 engages cam surfaces 343 on a drift-block 340, which is cammed in opposite directions by notches 341, 342 in the selector-bars 291, 292 as the latter move out of neutral positions. In the form shown in Fig. 9 an executive speed-changing lever 410, operating three selector-forks 414, 415. 416 is actuated by a mechanical remote-control including shaft 407 and a ball-mounted handlever 408 by means of which the shaft is turned to select and moved axially to establish a desired gear. The shaft 407 has selectivelypositioned cam-notches 461, which open a valve 455 whenever the shaft leaves a gear or neutral position, and send pressure-air from a reservoir 418 to a clutch-motor 409, so as to effect clutchdisengagement and subsequent re-engagement coincidenal with a gear-shift. The shaft 407 has additional cam-notches 475 in the second and third gear positions, in which positions the notches cause closure of a valve 471, through which the inlet pipe 421 of a speed -responsive clutch-control valve 417 communicates with the pressure-reservoir 418, so that the speed-responsive valve is effective for causing automatic clutch-disengagement in second and third speeds. The outlet pipe 422 of the speed-responsive valve 417 communicates with the clutch-motor 409 through the lower seating of the shifter-actuated valve 455, and included in the line 424, 426 connecting the valve 455 with the clutch-motor 409 is an additional snap-opening valve 425. The latter comprises a spring-loaded valve-member 481 the upper face of which is subjected to the pressure from the speed-responsive valve 417. The valve-member has on its upper face a skirt 482, so that when closed the area subjected to the speed-responsive pressure is less than that, viz, of a collar 483, which takes the pressure when the valve opens. By these means the valve 425 is caused to snap open at the desired pressure and remain open until the pressure falls considerably below that at which opening occurred. Closure of the valve 425 during clutch re-engagement is gradual, being always under the direct control of the speed responsive valve 417. The Specification as open to inspection under Sect. 91 describes also a modification wherein the means whereby the higher ratios render the speed - responsive declutching - means ineffective is omitted, clutch slip at low vehicle speeds in these, and other ratios, being prevented only by a snap-open valve similar to the valve 425, Fig. 9, such valve being arranged between the outlet of the speed-responsive valve and the shifter-actuated valve such a